Aromatic conductive polymers, such as polyaniline, polythiophene, and polypyrrole, seem useful because of their good stability and high conductivity but they are limited in the field of application because of their poor processability due to insolubility in organic solvents.
According to a recent report, it is possible to improve processability by dispersing the conductive polymer into water or an organic solvent such as aromatic solvent. (See Patent Document Nos. 1 and 2.)
Making the above-mentioned conductive polymer into a dispersion involves its conversion into an intrinsically conductive polymer by addition of a dopant and subsequent dispersion in water or a mixture of water and hydrophilic solvent. However, the complexity of these steps prevents the conductive polymer from being used in the form of coating material.
One way proposed to address this problem is by solvent substitution. (See Patent Document Nos. 3 and 4.) The method disclosed in Patent Document No. 3 is very complex because solvent substitution needs vigorous stirring.
There is a simple method for solvent substitution that involves deionization with an ion-exchange material. This method, however, is incapable of removing cations strongly adhered to the surface of particles of intrinsically conductive polymer, and hence it merely gives an unstable dispersion (with a water content no less than 1 wt %) of intrinsically conductive polymer in an organic solvent. (See Patent Document No. 4.)
The above-mentioned problems encountered in the prior art technology have to be solved to enlarge the application field of the conductive polymer, and hence there is a demand for a simple method for preparing an organic solvent dispersion of an intrinsically conductive polymer.
[Patent Document 1] JP-A-H7-90060
[Patent Document 2] JP-A-H2-500918
[Patent Document 3] JP-A-2004-532292
[Patent Document 4] JP-A-2004-532298